A throttle valve of this kind is known from DE 298 06 215 U1. There, the flow is controlled by having at least one flow-limiting aperture arranged in the wall of the bushing, which can be made to be congruent with a flow-limiting aperture arranged in the wall of a sleeve and connected to the header pipe, or be closed off in whole or in part.
Moreover, there is known from EP 0 797 080 a flow regulating valve with a flow meter, on which the valve-closing body exhibits a control edge which co-acts with the valve seat at the outlet nozzle, thus controlling the outlet cross-section.
Finally, EP 0 789 821 shows a valve device, particularly for controlling the liquid flow rate in a central heating or air conditioning system, in which two discs can be rotated against each other in 45-deg. steps for flow control. The apertures are neither tapering nor circular and do not allow a linear flow increase through a rotation of the two discs against each other. Instead, only pre-set flows, which result from combinations of the different openings of the one disc with the different openings of the other disc, can be achieved therewith; see table in FIG. 2 of said document. Practice has shown that it is not possible to achieve satisfactory regulation results therewith.